The moment Keith Evans signed a grant-in-aid last winter to play football at the University of Central Florida, Coach Gene McDowell inserted him into the starting lineup.

McDowell never had seen Evans play. He never had seen him practice. He never had seen him, period, until he visited the campus.

But McDowell knew that Evans, a sophomore transfer from the University of Michigan and former All-America safety at Fort Lauderdale St. Thomas Aquinas, would be a great addition to UCF's secondary.

''I always anticipated he would start,'' McDowell said. ''I based everything on his reputation.''

Not only has Evans lived up to that reputation, but he also has exceeded it. He already holds the Knights' single-season record for interceptions with five and is second on the team in tackles with 74 entering Saturday's homecoming game against Wofford College of Spartanburg, S.C., at 1 p.m. at Orlando Stadium.

Talk about an instant impact.

''I felt I was capable of making an immediate impact,'' Evans said, ''but I certainly didn't expect this kind of success right away.''

McDowell did.

''We haven't had a defensive back play more consistently since I've been here,'' said McDowell, in his second year as coach. ''He's got a chance to be the best defensive back UCF has ever had.

What makes Evans stand out?

''He understands our defensive concept better than most,'' McDowell said. ''He's a very smart tackler. He knows when to hit hard and when to wrestle a man down. He knows how to use his ability.''

Evans didn't have nearly as much time as his teammates to learn the defensive system. While the Knights were practicing last spring, Evans was earning his Associate of Arts degree at Broward Community College, where transferred in September 1985. He didn't join UCF until August 1986, three weeks before the season opener.

''Missing spring practice didn't really hurt me,'' Evans said with a slight lisp, the result of losing his four top front teeth during a football collision in high school. ''I have a pretty good football mind, so I can pick up things pretty quickly.''

Evans used that football mind to help to coach the team last fall at St. Thomas Aquinas, where he was discovered by former UCF assistant coach Bill Cubit. Cubit was recruiting linebacker Barry Brooks, who also signed with the Knights, when he bumped into Evans.

''He remembered me from high school,'' Evans said. ''He talked me into visiting, and I fell in love with the place.''

Evans, 20, chose UCF over several major colleges, including Pittsburgh, West Virginia and Boston College.

''I wanted to go some place close to home so my family could see me play,'' he said. ''They probably get a bigger thrill out of watching me play than I get out of playing.''

After leading St. Thomas Aquinas to four consecutive district and regional championships, Evans was recruited by several major colleges. A standout tailback, defensive back and punt returner -- he returned 12 punts for touchdowns -- Evans visited Florida, Notre Dame, Louisiana State and Michigan before deciding to sign with the Wolverines.

It was a big mistake.

Evans, 5 feet 11 and 191 pounds, sprained his ankle a week before the 1984 season opener and was redshirted. Then, after realizing how low he was on the depth chart and how long it might take him to reach the top, he left Michigan in May 1985 without playing a down.

''The mistake I made was that I chose the university for what it could do for me academically and after college rather than for its football program,'' Evans said. ''I kind of took football for granted.''

Evans does not consider UCF a step down.

''Our skill people are as good as those at any school in the country,'' he said. ''The only thing we don't have that the big schools have are big linemen.

''I still have aspirations of playing professional football, and just because I'm not at Michigan, it doesn't mean I can't make it. A lot of pro players come from small schools. If I'm good enough, they'll find me.''